In U.S. Pat. No. 3,886,899, the overspray problem is dealt with through the use of the mask system for shielding a portion of the article and its holding chuck from overspray of the powdered plastic compound in its movement through the article treatment zone. The mask system in the apparatus comprises complementary, counter rotating endless chains as carriers for pairs of shields. The paths of the carriers extend in parallel, side by side relationship through the article treating zone such that pairs of the shields assume a juxtaposed position encircling the upper portion of the article undergoing treatment, thereby shielding the upper portion of the article, the chuck mechanism carrying the article and the conveyor equipment therefor during the movement through a powder spraying booth located at one side of the mask or shield. In use of the pairs of shields through repeated cycles of spraying articles, some of the powdered compound adheres to the mask shield elements. Periodically, to avoid contamination of future articles to be sprayed, the mask shields must be cleaned. Heretofore, cleaning was done manually requiring shut-down of coating machinery, taking it out of production.
This problem is recognized in U.S. Pat. No. 3,909,289, in which the conveyor chucks are cleaned by a method of impinging a flame on the chucks for charring the compound, brushing the chucks and quenching them with water spray and thereafter directing a stream of air under pressure onto the chucks to remove the residue.